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AEBI 122 > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

autotrophs vs heterotrophs

A

autotrophs produce, heterotrophs consume (and depend on autotrophs directly or indirectly)
photoautotrophs use sun energy to make organic molecules

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2
Q

types of fuels

A

fossil fuels - non-renewable remains from organisms that died millions of years ago
bioethanol: ethanol from glucose from plant starch
biodiesel: plant oils from unicellular algae from in a photobioreactor

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3
Q

mesophyll cell contains

A

30-40 chloroplasts
main area of photosynthesis, many in leaves (green color)

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4
Q

structure of chloroplasts

A

2 interconnected membrane layers
inside lumen called stroma
inside stroma are stacks of thylakoids called grana
inside grana is thylakoid space

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5
Q

photosynthesis equation

A

6CO2 + 12H2O –> C6H12O6 + 6O2
CO2 is reduced to C6H12O6
H2O is oxidized to O2 (and H2O)

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6
Q

Carbon fixation

A

conversion of gaseous carbon to solid state carbon

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7
Q

Where does photosynthesis occur

A

light reactions happen in the thylakoid and calvin cycle happens in the stroma

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8
Q

visible light range
ideal light ranges for photosynthesis

A

380-750nm (purple, blue, green, yellow, orange, red)
purple, blue and red light

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9
Q

absorption spectrum vs action spectrum

A

graph plot of pigment light absorption vs wave length measured by spectrophotometer
graph plot of effectiveness in driving process vs wave length

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10
Q

how does a spectrophotometer work?

A

white light is separated through a prism into colors through a slit, a color is selected by adjusting the prism
color light passes through pigment sample and hits photoelectric tube changing light into electric energy for a galvanometer
high transmittance = low absorption

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11
Q

chlorophyll a, b and carotenoids

A

chlorophyll a - main photosynthetic pigment, CHO functional group
chlorophyll b - broadens photosynthetic spectrium, CH3 functional group
carotenoids - absorb excessive light that can damage chlorophyll

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12
Q

chlorophyll structure

A

porphyrin ring: light absorbing head of chlorophyll
with Mg2+ in the middle

hydrocarbon tail

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13
Q

how do pigments absorb light

A

when light hits pigment, electrons go to an unstable excited state, as they fall back down they release energy in the form of light/heat

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14
Q

light harvesting complexes

A

part of a photosystem, pigment molecules bound to protein transfer energy to reaction center

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15
Q

resonance energy transfer

A

transfer of light energy from one pigment molecule to another through electromagnetic interactions

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16
Q

Photosystem II overview

A

light hits chlorophyll pigments and gets bounced around until it reaches P680s
electrons go from p680s to pheophytin primary e acceptor
chlorophyll a absorbs max 680nm wavelength

17
Q

Photosystem I overview

A

absorbs max 700nm wavelengths
reaction center chlorophyll is call p700 (2)
primary electron acceptor is chlorophyll A0 (modified chlorophyll a)

18
Q

linear electron flow overview

A

primary pathway involving both photosystems
produces ATP and NADPH

19
Q

linear electron flow mechanism

A
  1. p680+ is strong oxidizing agent and splits water (O2 byproduct)
  2. from PSII primary e acceptor pheophytin e goes down electron transport chain through cytochrome complex
    (H+ are pumped into thylakoid space)
  3. ATP synthesis via photophosphorylation
  4. light excites PSI and P700 is oxidized by chlorophyll A0 to P700+
  5. electron from PSII replaces e for p700+
  6. from chlorophyll A0 e moves to ferredoxin
  7. e goes to NADP+ to form NADPH with high energy electrons (with H+ from stroma)
20
Q

cyclic electron flow overview

A

PSII not involved
no oxygen released
produces ATP but not NADPH (to satisfy calvin’s need of more ATP than NADH)
Light hits PSI, P700 passes e to chlorophyll A0, ferredoxin passes e to cytochrome c to go through photophosphorylation and produce ATP

21
Q

where are ATP and NADPH produced?

A

thylakoid membrane on the side facing the stroma (for access to calvin)

22
Q

Calvin input output

A

3CO2 in, 1 glyceraldehyde-3-phosphate (G3P) out
6 molecules circulate

23
Q

Carbon fixation phase of Calvin

A
  1. 3 CO2 (1 at a time) added to RuBP (ribulose bisphosphate)
    catalyzed by RuBP carboxylase-oxygenase (rubisco)
  2. 3 6-C intermediate breaks into 6 3-phosphoglycerate molecules
24
Q

Reduction phase Calvin

A
  1. 3-phosphoglycerate –> 1,3-bisphosphoglycerate + ADP
  2. 1,3-bisphosphoglycerate –> glyceraldehyde-3-phosphate + NADP+
  3. one G3P leaves cycle to be combined with another G3P and become glucose
25
Q

how many molecules of G3P are formed in Calvin

A

6, only one leaves the cycle

26
Q

RuBP regeneration phase Calvin

A
  1. 5 glyceraldehyde-3-phosphate + 3ATP –> 3 ribulose bisphosphate + 3 ADP
27
Q

which Calvin cycles used ATP or NADPH

A

ATP: 3. 3-phosphoglycerate –> 1,3-bisphosphoglycerate
6. glyceraldehyde-3-phosphate –> ribulose bisphosphate

NADPH: 4. 1,3-bisphosphoglycerate –> glyceraldehyde-3-phosphate

28
Q

stomata

A

stomata - pores that open for gas exchange in plants but can also lead to dehydration

29
Q

C3 plants

A

initial fixation of CO2 via rubisco

30
Q

photorespiration description

A

Rubisco will bind to O2 when stomata are closed
O2 will be consumed to burn sugar and release CO2
in Calvin this produces a 2-C molecules instead of 3

31
Q

advantage of photorespiration

A

limits damage of light reactions building up in the absence of the Calvin cycle
evolutionary relic of a time when atmosphere had little O2

32
Q

Downsides of photorespiration

A

on a hot day plants can burn 50% of carbon fixed (sugar) by calvin cycle
No ATP produced

33
Q

C4 plants and anatomy

A

incorporate CO2 into 4-C molecule
Increase CO2 concentration near rubisco to encourage carbon fixing
bundle sheath packed tightly around veins
mesophyll cells loosely packed

34
Q

C4 plant mechanism

A

4-C oxaloacetate produced by PEP-carboxylase
PEP-carboxylase has higher affinity for CO2 than rubisco, even with O2 around
oxaloacetate transported into bundle sheath (spatial separation) for calvin cycle with rubisco

35
Q

CAM plants mechanism

A

CAM = crassulacean acid metabolism (variation on C4)
Temporal separation: stomata open at night and take in CO2
4-C organic acids fixed from CO2
At night carbon is released from organic acids and put into calvin cycle

36
Q

percents types of plants

A

C3: 89% (wheat, pepper, rice, tomatoes)
C4: -1% (corn, sugarcane, sorghum)
CAM: -10% (succulents, cactus, pineapples, agave)

37
Q

excess sugar is stored as

A

roots, tubers, fruits, seeds

38
Q

total ATP and NADPH used in Calvin

A

9 ATP (6 and 3) and 6 NADPH

AEBI 122 (8 decks)

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